Analysis of blood culture trends has shown that the isolation of S. epidermidis from blood cultures of Clinical Center patients has been steadily and significantly increasing over the past 3-4 years. In an attempt to determine possible explantions for this increase, several parameters are being investigated in a prospective fashion. All patients with a blood culture positive for S. epidermidis have their records reviewed to establish, whenever possible, the following: 1) skin preparation before culture, 2) drawn by whom, 3) presence or absence of indwelling IV lines, 4) was the culture drawn through a line or peripherally, 5) other cultures, e.g. wounds, urines, cath tips, with S. epidermidis, 6) underlying disease and length of time in hospital, 7) antibiotics, if any, at the time of positive culture, 8) other blood cultures taken before or after the positive culture, and 9) was the patient treated for the organism. Ancillary studies also in progress that may also help to evaluate the significance of S. epidermidis blood culture isolates are: 1) attempts to phage type all isolates; 2) speciation of all isolates, 3) analysis of antibiotic susceptibility patterns; 4) silulated "plasma" cultures to check the role of laboratory contamination. CP-129.